Non-sterol products of the mevalonate pathway down regulate the pathway, in part, by inhibiting the translation of mRNA for and stimulating the degradation of 3-hydroxy-3-methylglutaryl coenzyme-A reductase (HMG-CoA reductase). In addition, this enzyme plays a key role in the cell cycle. The work proposed in this application will examine the mechanism of translational control of HMG-CoA reductase synthesis. The examination of translational control will begin with an extension of important preliminary data which demonstrates that sequences within the HMG-CoA reductase mRNA which code for the extensive membrane domain of the protein are sufficient for translational control of enzyme synthesis. In order to define the minimal cis elements within the coding region of the reductase mRNA which are sufficient for translational control, mutagenesis experiments will be conducted to alter the coding region and the consequences of these alterations on translation assessed after transfection into Chinese hamster ovary (CHO) cells. In order to identify, purify and study putative trans-acting regulatory factors that control translation in response to non-sterol regulators, like farnesyl acetate, an in vitro translation system which exhibits regulated translation of HMO-CoA reductase mRNA will be developed. Wheat germ translation extracts will be programmed with mRNA and CHO cell extracts will be tested for regulatory factors. Factors will be purified using translation and sequence specific gel-shift assays and interactions with the cis elements within the mRNA determined.